When manufacturing, e.g., a silicon wafer, a silicon single crystal ingot is sliced by a wire saw (see, e.g., Japanese Patent Application Laid-open No. 8-85053). FIG. 2 is a schematic view showing an example of a conventional wire saw. A wire saw 10 is an apparatus which allows a wire 1 (high-tensile steel wire) to travel at a high speed and presses an ingot 3 to be sliced (cut) while applying a slurry having GC (silicon carbide) abrasive grains dispersed in a liquid to this wire 1.
The wire is unreeled from one (right in this example) wire reel 7 to enter groove rollers 2 via a tension providing mechanism 4 formed of a dancer roller 4a including a dead weight 4b or a powder clutch 4c connected with a constant torque motor 4d or both the members. Each groove roller 2 is a roller obtained by press-fitting a polyurethane resin to a periphery of a cast steel cylinder and forming a groove on a surface of this cylinder at a fixed pitch, and the wire is wound around this roller for 300 to 400 turns and then taken up by the other wire reel 7 via the other tension providing mechanism 4. The wire is driven by a groove roller driving motor to reciprocate in a wire traveling direction 5 in a predetermined cycle. On the other hand, an ingot 3 is bonded to a slice beam 6, fixed to the wire saw through the slice beam 6, and pressed against the wire at a previously programmed ingot feed speed to be sliced.
On the other hand, a silicon wafer ((110) silicon wafer) having a crystal plane orientation (110) has preferable characteristics that its ID/VSD (inner conductance) is improved to substantially triple as compared with that in a regular (100) silicon wafer when manufacturing an MOSFET by using this (110) silicon wafer. However, a practical problem in a conventional technology is that a stable surface oxide film cannot be formed on a crystal plane having a plane orientation (110), and the (110) silicon wafer has not been exploited so far. However, a method for forming a stable surface oxide film irrespective of a crystal plane orientation (radical oxidation method) has been recently developed (see, e.g., Saito et al., “Advantage of Radical Oxidation for Improving Reliability of Ultra-Thin Gate Oxide”, 2000 Symposium on VLSI Technology, Honolulu, Hi., Jun. 13th-15th, 2000), and the (110) silicon wafer has suddenly come under the spotlight.
The (110) silicon wafer can be manufactured by using a wire saw to slice a silicon single crystal ingot having a plane orientation (110) that has grown in a crystal orientation [110] as a growth direction. However, its slicing yield ratio is lower than that of a silicon wafer having a plane orientation (100), and development of a method for stably obtaining the (110) silicon wafer has been desired.
It is to be noted that a slicing method that avoids cracks or breaking is disclosed in regard to a slicing method for a semiconductor single crystal ingot (see Japanese Patent Application Laid-open No. 9-262825).